"Why so many radical Muslims?" is an older question, recently-closed, which quite frankly is full of problems:
It's asking about why there are "so many" radical Muslims, and about why "so many" Muslims are taught to be violent, which is lacking in any sort of details. There is no reason to believe that any given (violent) Muslim in any given part of the world would have the same reason for their behaviour as any other, or that any given (violent) Muslim teacher would use the same reasoning in his teachings as any other. Without focussing on any particular group/teacher/etc, this is just opinion-based.
It is full of questionable claims, most notably the (irrelevant) claim that the Christian Trinity is not shirk, as well as the insinuation that violence is being taught by and to a majority of Muslims.
It is closed as off-topic; the question is clearly about culture and behaviour, but no indication is given in the question that this behaviour is actually Islamically based beyond the fact that it is practiced by "so many" Muslims.
It shows research effort, but is dismissive of the answers it has found without any indication of what it's actually looking for in an acceptable answer.
The actual question appears more rhetorical than practical, as evidenced by it being immediately asking why Muslims don't speak out against "these teachers" (again, without any specifics of who "these teachers" are) for being "wrong". It appears to be exactly the sort of "rant in disguise" that is actively discouraged on Stack Exchange in general.
It has already attracted pointless arguments (directly involving and in many cases directly instigated by the OP, which just adds weight to point 5 above) which has needed cleanup.
Frankly, the only value I see in the whole mess is the answer by Ansari, which spends as much time critiquing the question as it does answering it, basically explaining that this is far more sociopolitical than religious. Which basically just confirms that, yes, it is probably off-topic for this site.
Under the general Stack Exchange principle of answers (and questions) being useful to more than exactly one person, I am not entirely sure how valuable this answer even is to the site in the long run; the fundamental arguments are generally useful but the critique (and comment arguments) are pretty much only useful for exactly this question in exactly this form.
It seems to me that the whole thing should be abstracted out so that it's more generally applicable (which would probably involve a major overhaul of the question itself), cleaned up, and then probably locked to prevent further arguments from breaking out, but honestly I'm not sure it's even worth the effort (I'm personally inclined to just delete the whole thing rather than deal with it any more). Either way, it is in definite need of some form of curation.